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TELESCOPE OPERATIONS

CHANGING MASER REFERENCE

General

The normal timing standard used at Green bank is the Sigma Tau Maser. For pulsar and some other observations however, it is often beneficial to use the Rubidium timing standard instead. This is due to the Sigma Tau Maser's 28.75 Hz modulation which can corrupt some types of data collected.

Warning

The timing standard should only be changed when avoidance of the 28.75 Hz is desired AND it's specifically requested by the observer. The timing standard MUST be returned to the Sigma Tau Maser immediately upon completion of the observing program. The Sigma Tau Maser is the primary site reference.

Steps for changing the maser reference are outlined below. Contact electronics division personnel if problems are encountered during a reference change.

Changing Timing Reference to the Rubidium Standard

STEP ACTION
1 Go to the timing center and locate the short equipment rack labeled Rubidium Frequency Standard. It's located on the far right side.
2 Locate the control panel labeled Frequency Standards Switching Network.
3 Push in and rotate the Frequency Standards Switching Network's two rotary switches from position C to position A. The timing reference for ALL Green Bank site electronics is now set to the Rubidium standard. The only exception is the 1PPS and Site Time.
NOTE When using the Rubidium Standard, the 1PPS/5MHz SYNC fault will occur. This fault may be ignored.
4 Log an entry in the Timing Center Logbook showing the change made.
5 Update OpsLog as necessary.

Changing Timing Reference Back to the Sigma Tau Maser

STEP ACTION
1 Go to the timing center and locate the short equipment rack labeled Rubidium Frequency Standard. It's located on the far right side.
2 Locate the control panel labeled Frequency Standards Switching Network.
3 Push in and rotate the Frequency Standards Switching Network's two rotary switches from position A to position C. The timing reference for ALL Green Bank site electronics is now set back to its normal setting using the Sigma Tau Maser.
4 Log an entry in the Timing Center Logbook showing the change made.
5 Launch a Cleo LO application and reset the 1PPS/5MHz SYNC to clear its fault status.
6 Update OpsLog as necessary.

-- DavidRose - 4 Feb 2008

Topic ChangingMaserReference . { Edit | Attach | Ref-By | Printable | Diffs | r1.3 | > | r1.2 | > | r1.1 | More }
Revision r1.3 - 04 Feb 2008 - 21:14 GMT - DavidRose
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